In a wireless communications system, information transfer between a user equipment (user equipment, “UE” for short) and a radio access network (radio access network, “RAN” for short) is performed through an air interface (air interface, “air interface” for short). Because air interface resources (also called radio resources) are limited, radio resource management (radio resource management, “RRM” for short) has emerged at the right moment. Its basic goal is to improve network coverage and system capacity as much as possible under a premise of ensuring quality of service (quality of service, “QoS” for short) of an accessed service. To ensure the QoS of the accessed service, it is necessary to perform admission control (admission control) for a service request according to a usage condition of a resource, that is, to determine, according to a load condition of the system, whether to establish a bearer (bearer) for a new service request.
For a traditional wireless communications system, such as a Global System for Mobile Communications (global system for mobile communication, “GSM” for short) system or a Code Division Multiple Access (code division multiple access, “CDMA” for short) system, “dedicated use” is a major idea of resource allocation. Once a user accesses the system and a resource is allocated to the user, the resource is always occupied by the user, as long as a connection of the user is not interrupted. Therefore, resource usage (such as a power resource) is used to represent a load condition of the system. For example, when transmit power of a base station exceeds 90% of maximum transmit power, a cell load is considered to be high; otherwise, the cell load is considered to be low. In addition, because a resource is for dedicated use, prediction can be performed. That is, it may be predicted, according to a current load condition of the system, how many resources will be occupied by a new user after access.
A traditional method for admission control is to perform admission control mainly based on usage of system resources. First, it is necessary to calculate how many resources have been occupied in the current system, predict how many resources will be additionally occupied after the access of the new user, and finally compare a sum of the two with a preset admission threshold. If the sum of the two is lower than the admission threshold, a service request of the new user is admitted; otherwise, the service request of the new user is denied. However, with evolution of technologies, “sharing” has taken the place of “dedicated use” and become a mainstream of resource allocation. After a user accesses the system, a resource occupied by the user does not remain unchanged any longer, but is determined by a resource scheduling algorithm, allocated on demand, and balanced according to a priority. This makes it increasingly complex to calculate or predict resource usage of the system, and accordingly, it becomes more and more difficult to obtain accurate resource usage and an accurate admission threshold.